Polyurethaneureas are used to make "spandex," herein defined as a manufactured fiber in which the fiber-forming substance is a long-chain synthetic polymer comprised of at least 85% of a segmented polyurethane. Spandex, in turn, is used to make many articles of commerce, especially various types of clothing, including swimsuits, hosiery, intimate apparel, outerwear and the like. Polyurethaneureas also find use in molded and extruded products. Polyurethanes may be blended with other materials before being spun, molded, and/or extruded into products.
Polymers used in making spandex are themselves usually made by forming a prepolymer between a polymeric diol and a diisocyanate, and then reacting the resulting prepolymer with a diamine in a solvent such as N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) or dimethylformamide (DMF). (The aforementioned prepolymer is sometimes referred to as a "capped glycol.") The resulting polymer chains may then be extended by further reaction with one or more chain extenders, typically diamines. The chains may subsequently be terminated by the addition of a chain terminator, e.g., a monoamine. This chain terminator can be mixed with the chain extender or can be added separately, after the chain extender.
From an economic standpoint, it would be desirable to prepare polyurethaneureas, suitable for use in spandex and other applications, in the substantial absence of solvent, and to be able to either melt spin, solution spin, or isolate such polymers for later spinning.
Processes for making and using polyurethaneureas are well known to those skilled in the art. See H. Mark, et al., Ed., Encyclopedia of Polymer Science and Engineering, Vol. 6 (3d ed. John Wiley & Sons, Inc., New York 1986) at pages 733-755, and Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 10 (4th ed. John Wiley & Sons, Inc., New York 1993) at pages 624-638.
U.S. Pat. No. 3,480,456 describes the grinding of a thermoplastic coating materials in blenders, attritors and hammer mills at temperatures to -50.degree. C. using dry ice (solid CO.sub.2). Japanese Patent Application Publication 55-30,008 discloses a process for the preparation of thermoplastic polyurethane powder while adding dry ice immediately before, simultaneously, or immediately after adding the chain-propagating agent.